Republican Pennsylvania Congressman Ryan Costello announced Sunday that he will not seek re-election in November, boosting Democratic Party hopes of taking another seat, officials said.

Costello's announcement comes on the heels of a Democrat upset in a special congressional election March 13, in an area handily won by US President Donald Trump in 2016, prompting Republicans to sound alarm bells of more possible Democrat wins.

In that race, Republican Rick Saccone conceded his loss to Democrat Conor Lamb on March 21 in the razor-close race for the state's 18th Congressional District, a Republican stronghold.

Ryan Costello, R-Pa, participates in a mock swearing-in ceremony on Capitol Hill in Washington. Costello announced on Sunday, March 25, 2018, that he would not be seeking re-election, ending weeks of speculation about his future and boosting Democratic hopes of winning his House seat

Costello announced Sunday to Kasie Hunt, on the MSNBC program Kasie DC, that he will not seek re-election, citing both the redrawn suburban-Philadelphia district that now favors Democrats and his desire to spend more time with his family.

'It's the most difficult decision I can recall having to make,' he told Hunt on Sunday night.

He said in a statement to the news agency: 'We will work tirelessly to ensure this seat remains in Republican hands.'

Republican Pennsylvania Congressman Ryan Costello announced Sunday that he will not seek re-election in November, boosting Democratic Party hopes of taking another seat, officials said

The Democratic Congressional Campaign Committee said in a statement that other Republicans should take heed of Costello's decision.

Spokesman Evan Lukaske said: 'Costello's exit should set off alarm bells for vulnerable House Republicans, who will also have to explain to middle-class voters why the've given repeated handouts to the rich and biggest corporations, and who will face similarly tough, well-financed challenges from our deep field of impressive candidates,' said

Neither Costello nor his representatives were immediately available for comment.